Aetna (P) sued Murphy(D) to recover for damage he allegedly caused to a building that P had insured. D was a dentist in the building, and when he dismantled his office, it gave rise to a claim for damages. D was served with P's complaint on November 21, 1983, and gave no notice to Chubb until January 10, 1986. D filed a third-party complaint impleading his liability insurer, Chubb, as third-party defendant. Chubb moved for summary judgment because D inexcusably and unreasonably delayed in complying with the notice provisions of the insurance contract. It was granted, and D appealed. D contends that Chubb should not be excused if it suffered no prejudice by the delay.